The door_.Better repaired.a.isn't shut b.hasn't been shut 为何选b ,a 错在哪

问题描述:

The door_.Better repaired.
a.isn't shut b.hasn't been shut
为何选b ,a 错在哪

b的意思是这个门已经关不上了,最好修一下.
门关不上是过去时,已经发生的事情,所以不能选a.a是一般现在时